Range-Only UWB 6-D Pose Estimator for Micro UAVs: Performance Analysis

In recent years, ultra-wideband (UWB) technology has been widely used in indoor unmanned aerial vehicle (UAV) localization due to its high-precision ranging capabilities. Many localization schemes use multiple UWB devices onboard the UAV to correlate distance and orientation, demonstrating better resistance to magnetic field interference compared to relying solely on inertial measurement unit for orientation estimation. However, the precision achieved varies significantly among different approaches, and there lacks a unified metric to evaluate the performance of the estimation algorithms. In this work, we first derive an unconstrained Cramér–Rao Lower Bound (CRLB) for UAV pose estimation using range-only measurements. To assess the multiple effect of specified distance measurement errors on 6-D pose estimation accuracy, we leverage the CRLB to extend the conventional dilution of precision (DOP) concept and propose two physically meaningful orientation-coupled dilution of precision (ODOP) metrics. By utilizing the proposed ODOP metrics, we deduce their mathematical bounds and conduct a detailed analysis of the influence of tag, anchor, and pose distribution on the estimation performance. We evaluate the localization accuracy under various conditions to validate the technical findings.